2

I found a gdaldem color config:

3500 140 140 140
2500 209 209 209
1500 225 225 225
700 245 245 245
0 252 252 252
-32768 213 232 237 <=== What mean -32768
  • 3
    Wild guess: it probably means NoData. – ArMoraer Jan 22 '16 at 13:13
  • gdaldem documentation say: "The elevation value can be any floating point value, or the nv keyword for the nodata value" But what is the usage of "nodata value" and where is written -32768 ==> nodata value – Gerd Jan 22 '16 at 13:16
  • 1
    Yup, means nodata. If you want to redefine it, there are a number of posts here in GIS:SE such as How to redefine the nodata value into zero in QGIS?. @Gerd, you should provide a link to the documentation you got the quote from :) – Joseph Jan 22 '16 at 13:21
  • documentation: gdal.org/gdaldem.html – Gerd Jan 22 '16 at 13:24
  • 1
    @Gerd - My understanding is that nodata simply means that there is no data for the given area (i.e. absence of data). Usually nodata values are expressed with ridiculous numbers such as -32768 or -9999 etc. So yes, I believe you are correct although I'm not an expert so hopefully others can advise =) – Joseph Jan 22 '16 at 14:15
3
-32768  213 232 237

means: Take color "rgb 213 232 237" if in any area are no data for gdaldem color-relief rendering.

Remark: This question was result of my using NASA SRMT data from

http://dds.cr.usgs.gov/srtm/version2_1/SRTM3/Eurasia/*.

This SRMT data contain a lot of NODATA areas!

Better download NASA SRMT data from

http://srtm.csi.cgiar.org/SELECTION/inputCoord.asp

This data are complete. No NODATA areas!

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